1. Field of the Invention
The present invention relates to a beverage extracting apparatus for vending machines which mixes water and raw material of a beverage, filtrates the liquid mixture via a filter and extracts the filtrated liquid mixture.
2. Description of the Prior Art
A conventional beverage extracting apparatus for vending machines is shown in FIGS. 11 and 12 (Japanese Patent Publication SHO 62-211800). A liquid mixture of water, for example hot water, and the raw material of a beverage, for example a powder, is introduced into a cylinder 1 through an inflow port 1a. When a valve 2 opens the inflow port 1a, a bottom opening 1b is closed by a filter 4 moved vertically together by filter support 5 which is urged downwardly by a return spring 5a which also provides for the opening and closing of bottom opening 1b. After the liquid mixture is stored in cylinder 1, valve 2 is closed and pressurized air is supplied into the cylinder from a pressurized air generating means 3. The liquid mixture stored in cylinder 1 is forcibly filtrated and extracted by the pressure of the supplied pressurized air via filter 4.
The filter support drive mechanism 6 is constructed, for example, as shown in FIG. 12. Cam 6b is driven (rotated) by a motor 6a, driving force transmitting mechanism 6c is moved vertically by rotated cam 6b, and a lever 6e pivotably supported at a position 6f is rotated between the positions illustrated by the continuous line and the dashed line in FIG. 12 by engaging the bottom portion of driving force transmitting mechanism 6c with one end portion of lever 6e. The other end portion of lever 6e engages a lifting frame 6d attached to filter support 5. When lever 6e is rotated clockwise from the position shown by the continuous line to the position shown by the dashed line, filter support 5 is moved up together with lifting frame 6d and bottom opening 1b of cylinder 1 is closed by filter support 5 and filter 4 as shown in FIG. 11.
In such a conventional apparatus a very high accuracy is required for closing of the bottom opening 1b. Namely, if filter support 5 is moved up too far and the filter support is pressed too hard to the bottom of cylinder 1, an excessive load is applied to motor 6a. On the other hand, if filter support 5 is moved up too little and the force of the filter support on the bottom of cylinder 1 is too small, the liquid mixture in the cylinder to be filtrated leaks from bottom opening 1b to the outside when the pressurized air is supplied into the cylinder. Accordingly, the periphery shape of cam 6b, the length of driving force transmitting mechanism 6c and the length of lever 6e must be designed and processed with precision to achieve the proper movement and pressing force of filter support 5.
However, precision processing of the parts of the filter support drive mechanism increases the cost of manufacturing the apparatus. Moreover, since the installation error of the parts more or less occurs in the assembly of the apparatus even if the parts are processed with high accuracy, it is difficult to precisely set the movement amount and pressing force of filter support 5 to a target amount and a target force.